<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>下雨</title>
  <style>
    *{padding:0;margin:0}
    html{overflow:hidden}
  </style>
 </head>
 <body>
    <canvas id="canvas" style="background:#111" width="1600" height="809"></canvas>
    <audio src="1212.mp3" autoplay="" loop=""></audio>
    <script type="text/javascript">
        
        window.onload = function(){
            //获取画布对象
            var canvas = document.getElementById("canvas");
            //获取画布的上下文
            var context =canvas.getContext("2d");
            //获取浏览器屏幕的宽度和高度
            var W = window.innerWidth;
            var H = window.innerHeight;
            //设置canvas的宽度和高度
            canvas.width = W;
            canvas.height = H;
            //每个文字的字体大小
            var fontSize = 12;
            //计算列
            var colunms = Math.floor(W /fontSize);  
            //记录每列文字的y轴坐标
            var drops = [];
            //给每一个文字初始化一个起始点的位置
            for(var i=0;i<colunms;i++){
                drops.push(0);
            }
            
            //运动的文字
            var str = "我是笨蛋";
            //4:fillText(str,x,y);原理就是去更改y的坐标位置
            //绘画的函数
            function draw(){
                context.fillStyle = "rgba(0,0,0,0.05)";
                context.fillRect(0,0,W,H);
                //给字体设置样式
                context.font = "700 "+fontSize+"px  微软雅黑";
                //给字体添加颜色
                context.fillStyle = randColor();//可以rgb,hsl, 标准色，十六进制颜色
                //写入画布中
                for(var i=0;i<colunms;i++){
                    var index = Math.floor(Math.random() * str.length);
                    var x = i*fontSize;
                    var y = drops[i] *fontSize;
                    context.fillText(str[index],x,y);
                    //如果要改变时间，肯定就是改变每次他的起点
                    if(y >= canvas.height && Math.random() > 0.9){
                        drops[i] = 0;
                    }
                    drops[i]++;
                }
            };

            function randColor(){
                var r = Math.floor(Math.random() * 256);
                var g = Math.floor(Math.random() * 256);
                var b = Math.floor(Math.random() * 256);
                return "rgb("+r+","+g+","+b+")";
            }

            draw();
            setInterval(draw,30);
        };

    </script>
 

</body></html>